Mother visa rejected for second time

[mohamed2017]

Hello
I m on a tier 2 visa , and sent an invitation to sponsor my mother for a visitor 6m visa to visit me for 3 weeks however she got the application refused.
I submitted all evidence needed from me as sponsor and they were happy with that ,i also submitted her bank statement with a decent sum been for long time in the account ,plus HR letter from where she works.They noted the following points for rejection .
• Income from work not seen on bank statement.(As she receives that in cash and spend on living expenses)
• Deposits in the account are irregular and not equal to the claimed monthly income from work.(these deposits are from other source of income which is an agricultural land)

• No documentation that the additional monthly income from Savings (which i gave average for) is from the several bank term deposits she has.

• No documentation on source of funds in the bank. ( this is the biggest problem as her agricultural land which provides income was inherited long time ago with no legal paper proofs ,which is a common practice home)

• No documentation on personal and family circumstances.(she is a widow ,but my brother is living with his family in same city ...what sort of documents shall i present)
• No documents on assets in Egypt. (same problem with her agricultural land mentioned earlier)

What's your advice please since this is her second refused application ,the other one was 2 years ago before i arrived to UK.I thought sponsoring her would make things easier but it didn't help.